1. Field of the Invention
The invention relates to a heat sink and to a heat sink-equipped electronic component part.
2. Description of Related Art
Electronic component parts (e.g., a power module) constructed of semiconductor elements and the like are mounted in a vehicle such as a motor vehicle or the like. An electronic component part produces heat when in operation, and is therefore thermally connected to a heat sink.
A heat sink has a flow path that conveys a cooling medium that cools an electronic component part that is a heat-producing body. The flow path has two flow path wall surfaces that face each other. Of the two flow path wall surfaces, a flow path wall surface (cooling surface) at a side where the electronic component part is attached is provided with a plurality of fins.
A clearance for preventing interference during assembly of the heat sink is formed between distal ends of the plurality of fins and the flow path wall surface that faces the cooling surface (i.e., the opposite surface). Since this clearance has no obstacle that impedes the flow of the cooling medium, the cooling medium easily flows through the clearance. Therefore, since the cooling medium easily flows in the vicinity of the opposite surface, and less easily flows in the vicinity of the cooling surface, the cooling performance is not very good.
Hence, there is proposed a heat sink in which the opposite surface is provided with a plurality of protrusions in the shape of waves in order to impede the flow of the cooling medium in the vicinity of the opposite surface (see, e.g., Japanese Patent Application Publication No. 2007-110025 (JP-A-2007-110025)). These wavy protrusions are provided so that the summit of each protrusion is positioned between the distal ends of fins.
Another heat sink in which protrusions whose vertical sectional shape is triangular are arranged so as to meander (or zigzag) for another purpose has been proposed (see, e.g., Japanese Patent No. 4027353). The protrusions are provided for three-dimensionally stirring the flow of the cooling medium and causing the cooling medium to strike the cooling surface. The protrusions, according to, for example, Japanese Patent No. 4027353, may be provided on both the cooling surface and the opposite surface. In this case, the heat transfer area of the heat sink, which transfers heat to the cooling medium, increases, and the narrowed flow paths cause the cooling medium to flow faster.
However, in the heat sink described in Japanese Patent Application Publication No. 2007-110025 (JP-A-2007-110025), since there is no obstacle that impedes the flow of the cooling medium in recesses that are trough portions of the wavy protrusions provided on the opposite surface, the cooling medium easily flows in the recesses. Therefore, in the vicinity of the opposite surface; the effect of impeding the flow of the cooling medium is not sufficient, and therefore the cooling performance is not sufficient.
Besides, the heat sink described in Japanese Patent No. 4027353 has the following problems (1) to (2). (1) Since the cooling surface has no protrusion, or if any, the vertical sectional shape thereof is triangular, the heat transfer area of the heat sink, which transfers heat to the cooling medium, is small. (2) In the case where protrusions are formed on both the cooling surface and the opposite surface so as to narrow the flow path, the amount of change in the flow rate with respect to the dimensional error of the flow path is large, and therefore the variation in the cooling performance and the variation in the pressure loss are large.